At present, the water resources in the world are in scarcity and a lot of areas lack of water. In a lot of areas lacking of water, people lack of both drinking water and water for life and production. In order to solve the problem of water scarcity in these areas, wells are dug in a lot of areas; however, the groundwater in these areas is also in scarcity, so the water in the wells often comes from rainwater, river water and the like, which is not filtered and is not applicable to drinking. Although water which has been deposited for a long time can become clear, the water has smells and deteriorates in a long time. However, water in wells permeates into the soil or is evaporated fast. In this way, rainwater can not be used well.
In addition, some water for life such as water from washing cars in car washing rooms, or watering flowers or cleaning plazas is often drained through underground watercourses and is not utilized well, thus causing considerable waste of water.